We had been considering solar for a while and a local co-op brought prices down to what I consider a reasonable payback range so we finally pulled the trigger on a grid-connected PV array for our roof. Our house has electric everything and based on last years usage and the installers estimates (confirmed by PV watts within 5%) the array should offset roughly 50% of our annual power requirements.

I am in the process of deciding between 2 net-metering billing options offered by Dominion Virginia Power. One is a flat rate 11c/kWh with a base charge of $7/month, the other is a TOU plan with time of day and seasonal changes and a base rate of $12 per month. The base rate is paid regardless of whether or not we produce more than we use that month.

We were previously on a "whole house" EV TOU plan and that came out to be basically a wash, I think we paid an average of 10.7c per kWh instead of the standard 11c/kWh. The 5c/kWh we paid to charge the leaf overnight was offset by the 16c/kWh we paid to run the AC and oven in the afternoon and evening.

I have downloaded our usage data from last year and used PV watts to estimate our annual hourly production. A simple subtraction in excel shows our estimated net use but the demand TOU rate schedule from Dominion is so convoluted with riders and demand charges that I can't predict what our exact rate will be for a given window. But given the fact that over 50% of our electricity use is the leaf and the water heater, both of which are on a timer, I think it could probably work for us.

Anyone have experience with a TOU plan in Virginia with net metering, a PV array, and an EV? Did it benefit you? Was it pretty much a wash? Did you come out ahead?

I have looked at TOU and adding solar but have not done either yet. In your situation, it looks like you are considering schedule 1 or 1s based on your descriptions. Schedule 1ev has a larger set of TOU categories which could be a favorable option if it is allowed with RE net metering. Another option you may want to look at is Schedule 1 plus schedule ev, which is a separate meter, generally after your s1 meter that just your EVSE is hooked up to. I considered doing the s1 + ev but I tend to do free public charging a mile from work often enough that it did not make much of a difference for me.

Bottom line, you need to get a decent idea of how much you are producing or using during each time period that a possible TOU rate covers and just compare each option in a spreadsheet.

BillHolz wrote:I have looked at TOU and adding solar but have not done either yet. In your situation, it looks like you are considering schedule 1 or 1s based on your descriptions. Schedule 1ev has a larger set of TOU categories which could be a favorable option if it is allowed with RE net metering. Another option you may want to look at is Schedule 1 plus schedule ev, which is a separate meter, generally after your s1 meter that just your EVSE is hooked up to. I considered doing the s1 + ev but I tend to do free public charging a mile from work often enough that it did not make much of a difference for me.

Bottom line, you need to get a decent idea of how much you are producing or using during each time period that a possible TOU rate covers and just compare each option in a spreadsheet.

I appreciate the thoughts. I am currently on Schedule1-EV which is a whole house TOU plan. I did not like the separate meter option because of the costs involved with installing a second meter and the flat monthly fee involved with the second connection.

Unfortunately, net metering is only compatible with schedule1 and schedule 1s. I cannot remain on my schedul1-ev plan with net metering. If I could I would make a fortune...

Schedule1s has a demand component that I cannot predict because they assess that based on the highest load periods during on peak hours of the current billing month. In other words, they choose after the fact. This makes it impossible for me to simply compare in a spreadsheet with much precision.

I can assume that, in the summer, highest demand will be during sunny hot afternoons when A/C demand is highest and feel fairly confident that my solar production will offset much of that. But I can't be sure in the non-summer months because most of my solar production will be during off-peak hours that time of year.

That's why I was hoping someone had some real world experience with this...

golfcart wrote:We had been considering solar for a while and a local co-op brought prices down to what I consider a reasonable payback range so we finally pulled the trigger on a grid-connected PV array for our roof. Our house has electric everything and based on last years usage and the installers estimates (confirmed by PV watts within 5%) the array should offset roughly 50% of our annual power requirements.

Congratulations!

I will note here that my system typically outperforms PVWatts by about 25%. Of course, that depends a bit on your assumptions.

I'm in VA, but our part of the grid was sold to a small co-op about ten years back. We do not have "real" TOU here.

Here are some thoughts:- Are you willing to share a year's worth of hourly usage data with me for my new spreadsheet? In return, I will add your house data into the spreadsheet which will allow you to play what-ifs including various amounts of solar, EVs and batteries. I'm also willing to explore the possibility of adding some TOU calculation capabilities into the spreadsheet if I can figure out a way to implement it. We can then adjust as your actual data comes in.- If you go with a TOU plan initially, you will be able to easily compare your results with a flat-rate plan later. OTOH, if you go with a flat-rate plan now, you will never *really* know if you would have saved money with the TOU plan (unless Dominion Power provides a calculator that you can trust).- If you do not have a heat-pump water heater, I recommend that the next time you make a replacement. It can save as much as 4 MWh/year.- Your daytime consumption due to air conditioning is likely to be very low because when you need air conditioning is often the same time the sun is shining. (Evening is a different matter.)- If you are installing an Enphase system, please let me know the location of your system's website so I can add it to the MTBF spreadsheet.- I think the following statement that you made typifies the real issues with TOU metering. I have come to believe that TOU rates are designed to induce customers to better match the power company's production curve WITHOUT ACTUALLY PAYING THEM TO DO SO. This is accomplished by obfuscating the details to the point where the benefit is much smaller than it appears or even ends up costing more.

golfcart wrote:A simple subtraction in excel shows our estimated net use but the demand TOU rate schedule from Dominion is so convoluted with riders and demand charges that I can't predict what our exact rate will be for a given window. But given the fact that over 50% of our electricity use is the leaf and the water heater, both of which are on a timer, I think it could probably work for us.

golfcart wrote:We had been considering solar for a while and a local co-op brought prices down to what I consider a reasonable payback range so we finally pulled the trigger on a grid-connected PV array for our roof. Our house has electric everything and based on last years usage and the installers estimates (confirmed by PV watts within 5%) the array should offset roughly 50% of our annual power requirements.

Congratulations!

I will note here that my system typically outperforms PVWatts by about 25%. Of course, that depends a bit on your assumptions.

I'm in VA, but our part of the grid was sold to a small co-op about ten years back. We do not have "real" TOU here.

Here are some thoughts:- Are you willing to share a year's worth of hourly usage data with me for my new spreadsheet? In return, I will add your house data into the spreadsheet which will allow you to play what-ifs including various amounts of solar, EVs and batteries. I'm also willing to explore the possibility of adding some TOU calculation capabilities into the spreadsheet if I can figure out a way to implement it. We can then adjust as your actual data comes in.- If you go with a TOU plan initially, you will be able to easily compare your results with a flat-rate plan later. OTOH, if you go with a flat-rate plan now, you will never *really* know if you would have saved money with the TOU plan (unless Dominion Power provides a calculator that you can trust).- If you do not have a heat-pump water heater, I recommend that the next time you make a replacement. It can save as much as 4 MWh/year.- Your daytime consumption due to air conditioning is likely to be very low because when you need air conditioning is often the same time the sun is shining. (Evening is a different matter.)- If you are installing an Enphase system, please let me know the location of your system's website so I can add it to the MTBF spreadsheet.- I think the following statement that you made typifies the real issues with TOU metering. I have come to believe that TOU rates are designed to induce customers to better match the power company's production curve WITHOUT ACTUALLY PAYING THEM TO DO SO. This is accomplished by obfuscating the details to the point where the benefit is much smaller than it appears or even ends up costing more.

golfcart wrote:A simple subtraction in excel shows our estimated net use but the demand TOU rate schedule from Dominion is so convoluted with riders and demand charges that I can't predict what our exact rate will be for a given window. But given the fact that over 50% of our electricity use is the leaf and the water heater, both of which are on a timer, I think it could probably work for us.

I have no issue sharing my usage data if you think it has some value.

I appreciate the offer with your sheet but I really don't need a sheet to implement TOU scenarios I am confident I can handle that myself either with excel or with Python. I already basically did it in excel I just can't anticipate all of Dominions riders or when Dominion is gonna add on a demand surcharge ahead of time so I'd just have to take educated guesses.

I can't really see a scenario where the TOU plan is a huge net loss and can think of a lot of scenarios where I come out ahead so I feel like it is a reasonable risk. I agree that there is also value in doing the TOU for comparisons sake and if after a year I don't like it I can always switch to a flat rate net metering schedule.

Thanks for the heads up on the water heater, ours is only 4 years old though so I doubt we'll replace it soon.

Good to hear about you outperforming PVWATTS. Our system uses a solar edge inverter and optimizers with axitec panels. 5.83 kW system at 215 degrees and a 20 degree tilt. Should be oriented well for the TOU plan in the summer which puts a premium on afternoon demand.

We've been up and running for a week. The last few days have been great I'm averaging about 33kWh a day with the cold weather and clear skies. At this rate we will cover all of my transportation needs easily with the panels, even on cloudy days I've been getting 15kWh out of it. I am addicted to monitoring the output of the panels with my mobile app...

If you already have a dedicated EVSE circuit, adding a schedule ev meter that is subtracted from your schedule 1 net metered house would only cost the price of the meter base, the permit, and a small amount of additional wire. No need for an electrician if you are at all handy with wiring.

The combined base charge is less than on 1s and gives you the benefit of TOU on the big controllable usage, charging your car.

BillHolz wrote:If you already have a dedicated EVSE circuit, adding a schedule ev meter that is subtracted from your schedule 1 net metered house would only cost the price of the meter base, the permit, and a small amount of additional wire. No need for an electrician if you are at all handy with wiring.

The combined base charge is less than on 1s and gives you the benefit of TOU on the big controllable usage, charging your car.

My understanding from speaking directly with dominion is that the ev plans are not compatible with a net metering plan although there may be something of that nature in the future. Since my system is large enough to be pushing out to the grid during the afternoon most days I need some sort of net metering which limits me to schedule1 or schedule1s. If I am wrong about that then certainly I may consider that option.

There were 2 issues for me involving the second meter. One is that I actually have 2 plugs where I charge and would like to retain both so that my wife and I can charge simultaneously. Second, when i spoke with my electrician it would have been a few hundred dollars additional to get the dedicated meter installed and that is not something I am confident doing myself. I did the math and it would have taken quite a long time to recoup the cost of the extra meter installation.

golfcart wrote:I have no issue sharing my usage data if you think it has some value.

Thanks! I'll PM you next week when I get back to that project. BTW, how many kWh does your house consume in a year?

golfcart wrote:I appreciate the offer with your sheet but I really don't need a sheet to implement TOU scenarios I am confident I can handle that myself either with excel or with Python. I already basically did it in excel I just can't anticipate all of Dominions riders or when Dominion is gonna add on a demand surcharge ahead of time so I'd just have to take educated guesses.

Yeah, it's not too difficult. The main thrust of my sheet is to allow you to see the impact of batteries for the eventual day when net metering goes away in VA. Perhaps I'll take a look at Dominion's website to see what your TOU rates look like.

golfcart wrote:Good to hear about you outperforming PVWATTS. Our system uses a solar edge inverter and optimizers with axitec panels.

Solar Edge should perform similarly to Enphase. I'm guessing you didn't get the new HD Wave inverter because it appears those only go up to 3.68 kVA currently. Does your inverter have a plug to allow you to get some AC power when the sun is shining, or is that only on the HD Wave?

golfcart wrote:5.83 kW system at 215 degrees and a 20 degree tilt. Should be oriented well for the TOU plan in the summer which puts a premium on afternoon demand.

Agreed. Mine are at 30 degree tilt and 194 degrees azimuth. In other words, optimized for about 1:00 PM, which works very well. Yours are optimized at about 2:15 PM, which should also work very well. The flat angle means your production will be outstanding in summertime. Here is a good website to see how close you are to optimum pointing: Solmetric. I put in "Newport News" and it appears you are within 5% of the optimum production for your location.

golfcart wrote:We've been up and running for a week. The last few days have been great I'm averaging about 33kWh a day with the cold weather and clear skies. At this rate we will cover all of my transportation needs easily with the panels, even on cloudy days I've been getting 15kWh out of it. I am addicted to monitoring the output of the panels with my mobile app...

We used about 15000kWh last year, 80% of which seems to be the leaf, water heater, and HVAC. I use about 15kWh per day for my 50 mile rt commute about 15-20 days a month. In May, where the HVAC didn't kick on much we only used about 800kWh total. In January it was more like 1800kWh.

Dominion should be installing our new meter next week so we'll start net metering at that point. I talked with our installer yesterday and told him that we wanted to go with the demand TOU plan called schedule 1s. We'll see how it goes.

Our inverter is a SE5000 series single phase inverter with a 12yr warranty. I don't recall seeing anything about a plug in the manual.

Just to update, I did 3 months on the TOU plan and it was clear that it is not a good value the way Dominion VA power has it structured.

Despite putting the water heater on a timer and charging my car overnight, the TOU plan was $10 - $15 higher than a standard schedule plan would have been based on the Dominion worksheet I downloaded.

There were 2 reasons the TOU plan (schedule 1-s) was consistently higher than the regular net-metering plan (schedule 1).

1) Schedule 1s had a base charge of $12 per month vs $7 for schedule1. This threw you in a $5 hole every month right from the start.

2) Schedule 1s incorporates generation and distribution "demand" charges which hit you hard if you use a lot of electricity during any 30-minute on-peak window the entire month. My "demand" charges were as much as my entire bill last month. See below for determination of "demand" charges.

III. DETERMINATION OF DISTRIBUTION DEMANDThe kW of demand will be determined as the highest average kW load measured in any 30-minute interval during the on-peak hours of the current billing month.

Generation Demand Chargea. For the billing months of June – September All On-peak kW of ES Demand @ $4.070 per kWb. For the billing months of October – May All On-peak kW of ES Demand @ $2.334 per kWc. Plus Distribution Demand Charge All On-peak kW of Demand @ $1.612 per kW

Long story short I changed back to a regular net-metering schedule1 plan before I wasted any more money on these "demand" charges. I can't stop cooking dinner and running the A/C during peak hours and it only takes 30 minutes of high use in any given month to result in a huge "demand" charge.